Method of in-vivo measurement of fat content of a body and apparatus therefor

ABSTRACT

A method of in-vivo fat measurement of humans or animals by scanning the ear of the subject using a fibre optic probe delivering a light beam of Near infrared wavelengths provided by a NIR source. Passing the beam through an interferometer to encode data from the whole spectral range simultaneously. Detecting reflected light by a detector and applying Fourier Transform techniques to determine the intensity of the light in at least one narrow wave band selected for its correspondence to a form of fat. Recording the NIR response and determining the fat content of the body by either comparison to known reference samples or by use of an empirical formula.

FIELD OF THE INVENTION

[0001] The invention relates to a method for the in-vivo measurement offat content of a body, such as a human or an animal, by the use of lightin the near infrared region of the light spectrum, and the apparatus formeasurement of body fat.

BACKGROUND OF THE INVENTION

[0002] Measurement of body fat in humans is one of the factors inchecking the fitness and general health level of humans. Excess fat isknown to be a risk factor with regard to heart disease, diabetes, andeven cancer of certain kinds. Excess fat has recently come under a highdegree of scrutiny by the health industry, and it is desirable to beable to make an accurate measurement of body fat in order to assesshealth risks.

[0003] Obesity is currently defined by a “body mass index” or BMI. A BMIof more than 27, according to Health Canada guidelines, is regarded asobese. However, recent reports suggest that the use of the BMI aloneleads to two common forms of misclassification. The first is of a highlymuscular individual with a high BMI who may be classified as “overfat”,when, in fact he/she is not. The second is of individuals with a healthyBMI (18.5 to 24.9) who actually do have an elevated body fat content andare at risk.

[0004] Another method for classifying body fat content is the densitymeasurement. The percent body fat is calculated by an equation based onthe density of the body. The density of the body is calculated by anequation that involves measuring a person suspended on a trapeze in theair, and then weighing the same person under water.

[0005] The equipment used for this measurement includes a special weighscale, and a submersion pool or tank. Some of the drawbacks of thissystem are that the standard body density used for comparison is that ofa young Caucasian. Modifications in the equations may be necessary forpersons of other ethnic origins. In addition, some people feeluncomfortable when they must be fully submerged, leading to incorrectreadings, the procedure requires a trained operator, and there is alwaysair left in the lungs, and it is difficult to correct for this residualair accurately.

[0006] To date the usual and the cheapest method of fat measurement isconducted by a pair of calipers. The ends of the calipers are simplysqueezed against a fold of the skin, at certain selected locations onthe body. This system gives variable and erratic results, and is knownto be unsatisfactory.

[0007] Systems for measurement of body fat have been proposed using nearinfrared light. One such proposal is described in experimental form in“A New Approach for the Estimation of Body Composition: InfraredInteractance”, by Conway J et al, American Journal of Clinical Nutrition40: December 1984, pages 1123 to 1130. Systems have been proposed inpatent literature using near infrared light. One such system isdescribed in U.S. Pat. No. 4,928,014, R D Rosenthal, dated May 22, 1990.

[0008] This system was later found to be unsatisfactory and unreliable.

[0009] Another system for the measurement of body fat is the systemknown as magnetic resonance imaging (MRI). This system provides muchmore accurate results than any other system known, at present. However,the equipment is a major investment, in the order of millions ofdollars. The operation of it requires a highly trained team of medicalassistants. The entire system takes a relatively long time to scan aperson. As a result the per person costs of MRI are too high to enableit to be used simply for body fat measurement.

[0010] Another system is the Deuterium Oxide Dilution system, but thisis also a technical and demanding system, and is not satisfactory foruse in every day medical practice, or in fitness testing.

[0011] However, when a doctor is carrying out a physical exam of aperson, which may be required for insurance, or for admission to certaintypes of employment, or which may be required by the individual for anannual monitoring of health, some form of measurement of fat content isusually carried out, as part of the overall tests used to evaluate thestate of health of the individual.

[0012] Consequently, even though it is well known to be inaccurate, thestandard test for evaluating the fat content of the human body has, formany years, been the skin fold caliper test.

[0013] There are three distinct categories for human fat. These arestructural, metabolic and storage fats. Structural fats form part ofeach and every cell of the body, mainly in the cell membrane. Metabolicfats are a group of lipids that are used in metabolic processes. Storagefats represent the largest component of human fat. Part of the storagefat is found in the subcutaneous layer of the skin which is the thirdlayer of skin found beneath the epidermis and dermis layers. Theremaining smaller part of storage fat is used as a cushion for thevisceral organs (liver, heart, kidneys, etc.).

[0014] There are several different types of fat found in the human body.Some occur naturally, others are only attainable by diet. Briefly, thetypes of fat are saturated fats, unsaturated fats, phospholipids andtriglycerides.

[0015] Saturated fats are commonly found in animal fat products such asbutter, lard and animal meats. Unsaturated fats, are divided into twogroups, mono or poly unsaturated fats. An example of a monounsaturatedfat is Oleic acid and can be found in olive oil. Polyunsaturated fatsare essential fatty acids and are only attainable through diet. Examplesof polyunsaturated fats are linoleic acid, linolenic and arachidonicacids. These are essential fatty acids and may be found in soy bean oil,peanut oil and corn oil to name a few.

[0016] Phospholipid, the most common of which is lecithin, is animportant common component of all cell membranes.

[0017] Triglycerides, composed of three fatty acids attached to glycerolmolecule and are the storage form of fat that occurs when humans eatcalories in excess of their energy needs.

[0018] In the case of cattle carcasses, fat content has been measured inthe carcass of the dead animal using a needle probe inserted into thecarcass. This system has given satisfactory results. However, it is ofuse only after the animal has been slaughtered. Clearly it is of no useto humans. Even for animals, it gave a reading which was after the fact.By the time the measurement was available, it was then too late to makeany attempt to correct the fat content of the animal by altering thediet. Fat content of animal carcasses is a major factor in the price forthe carcasses received by the farmer. Market considerations require thecarcass to have a low fat content. If the fat content is excessive thenthe farmer will receive less for the animals than if the fat content islower.

[0019] Where animals are being raised for slaughter it would bepreferable to be able to monitor the fat content of the animals in-vivoas they were being raised. If testing were available in-vivo the animalsdiet could be adjusted to maintain a desirable low fat content. Howevermeasurement of animal fat content, while the animal is alive, cannot bedone with the invasive, needle probe type of measurement system.

[0020] Near Infrared (NIR) Spectroscopy, with its non-invasive, in-vivocapabilities can solve this problem. It is useful in examining aqueoussolutions and mixtures, as well as biological studies. The interest innear infrared spectroscopy, for the analysis of chemicals, stems from anumber of factors. Absorptions in the near infrared region arise fromvibrational transitions to the second or higher energy states. Becauseof the very low probability of such transitions, absorption intensitiesare several orders of magnitude below those of the correspondingfundamental vibrations in the infrared and/or ultraviolet (UV) region ofoptical spectrum. Consequently infrared is not as sensitive in analysisof species present at low concentrations. Additionally, near infraredspectroscopy has the advantage that aqueous solutions can be readilyanalyzed without much interference from water absorption.

[0021] The intense absorption of near infrared wavelengths, by aspecies, also allows them to penetrate a sample sufficiently to beuseful in the analysis of thicker samples, such as body tissue.

[0022] The use of light in the near infrared region of light spectrumfor purposes of analysing for certain chemicals or for creating “images”is discussed in U.S. Pat. No. 5,440,388, R Erickson, dated August 8,1995. In this patent, there are descriptions of numerous different typesof technology, all of which are mentioned incidentally, in passing. Theactual invention described relates to a piece of equipment in whichthere are a plurality of discrete light sources each producingmonochromatic light of a specific wavelength, the light sources beingcombined into a single beam of light. An interferometer modulates thelight beam and a detector detects each of the discrete wavelengths. Thisis different than using Fourier Transform Near Infrared (FT-NIR)Spectroscopy. The FT-NIR instrument makes use of an interferometer toencode data from the whole spectral range simultaneously. The Michelsoninterferometer is used to produce a signal of a lower frequency than thefrequency emitted from the NIR source. The lower frequency contains thesame information as the original radiation signal, but is converted to aspeed slow enough for detection by a detector. The output of theinterferometer is an interferogram of all wavelengths emitted by thesource. A computer then performs the Fast Fourier Transform of theinterferogram and results in a frequency domain trace.

[0023] Fourier Transform Near Infrared Spectroscopy has certainadvantages over traditional spectroscopy, in which the response of asample to light is measured by scanning sequentially over a range ofwavelengths. Fourier Transform Near Infrared Spectroscopy measures theresponse of the sample to all the wavelengths of interestsimultaneously, by measuring the light after it interacts with thesample and recording the entire spectrum at once.

[0024] In the description of '388, it is stated that for variousdifferent samples, the light sources will have to be changed and thedetectors will also have to be changed. This system is an array of lightsources of specific wavelengths and an array of detectors for detectingsuch wavelengths. The system must therefore be specified for theparticular chemical being analysed, or the nature of the specific samplebeing imaged.

[0025] The system described in '388 is not suitable for measurement ofbody fat because it does not provide any details on its resolution oraccuracy or its ability for chemical analysis. This is different thanusing FT-NIR spectroscopy. The FT-NIR spectrometer, which, by contrast,makes use of an interferometer to encode data from the whole spectralrange simultaneously. The description of '388 is focussed on imagingrather than chemical composition of the material. There is one statementin the description of '388 which appears to be inaccurate, where itspeaks of; “Near infrared spectroscopy was applied to human skin in the1950's, and has since been developed for transcutaneous measurements ofbody fat composition.”

[0026] There is no reference in the description for this assertion. Inspite of a careful search of the literature, no such reference can befound.

[0027] It is desirable to provide a method of measurement of fat contentof a body, whether human or animal, which is simple, accurate, andeconomical and which is non-invasive, and can be carried out in-vivoquickly, with lower cost equipment and with a minimum of training.

BRIEF SUMMARY OF THE INVENTION

[0028] With a view to providing a system for the in-vivo measurement offat content of a body, the invention provides a method of in-vivomeasurement of the fat content of a body containing at least one form offatty acid having a reflectance characteristic corresponding to a narrowwave band of light in the near-infrared region of the spectrum,comprising the steps of providing a NIR-source emitting a laser lightbeam of near infrared intensity and passing said beam through aninterferometer to encode data from the whole spectral rangesimultaneously; applying the near infrared beam through a fibre opticprobe to a selected portion of the body having a relatively thin skinlayer over a layer of cartilage; directing the reflected light beam fromthe skin to a detector; and next analysing the reflected light byFourier Transform techniques to determine the intensity of light in atleast one narrow wave band selected for its correspondence to a form offat. In the preferred embodiment, the intensity of the reflected lightis compared in that wave band with the reflective characteristics ofreference materials with known fat content in said wave band, andthereby evaluating the fat content of the body.

[0029] In another embodiment, the second fat content measurementinvolves quantitative measurements using the physical parameters ofheight, weight and age of the subjects, along with the NIR response inan empirical equation to determine the total body fat content of humans.

[0030] The various features of novelty which characterize the inventionare pointed out with more particularity in the claims annexed to andforming a part of this disclosure. For a better understanding of theinvention, its operating advantages and specific objects attained by itsuse, reference should be made to the accompanying drawings anddescriptive matter in which there are illustrated and describedpreferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 illustrates a schematic of a fibre optic probe,

[0032]FIG. 2 illustrates the positioning of the fibre optic probe forscanning of the subject,

[0033]FIG. 3 illustrates a calibration curve of the NIR responses ofreference samples plotted against the known percent fat content of thereferences,

[0034]FIG. 4 illustrates the NIR results of reference mixtures and NIRempirical equation for female and male,

[0035]FIG. 5 illustrates a comparison of NIR results for femalevolunteers and NIR reference samples,

[0036]FIG. 6 illustrates a comparison of NIR results for male volunteersand NIR reference samples

[0037]FIG. 7 illustrates a comparison of NIR empirical equation resultsand MRI results.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0038] The invention provides a method for determining the total fatcontent of the body using Fourier Transform Near infrared (FT-NIR)spectrometer and various calculations.

[0039] The present invention illustrated herein is a method of scanningand evaluating total body fat content in humans using non-invasive andin-vivo FT-NIR spectroscopy. Although the following outlines testing forhumans, modifications may be made for testing of animals and fat contentin animals.

[0040] The FT-NIR spectroscopy has a much higher resolution and accuracylevel than Near Infrared (NIR) spectrometers. The FT-NIR spectrometerhas a spectral resolution of 0.3 nm (2 cm⁻¹ at 8000 cm⁻¹) whereas othergrating or filter instruments are between 2 nm (5 cm⁻¹ at 5000 cm⁻¹) to10 nm (25 cm⁻¹ at 5000 cm⁻¹).

[0041] Dispersive instruments operate in a frequency domain whereas theFourier Transformed NIR Infrared (FT-NIR) may be operated in thefrequency domain or a time domain. The advantage of operating in a timedomain allows for faster results.

[0042] Near infrared wavelengths of light are absorbed by species due todistinctive molecular vibrations and low level electronic excitations.Many molecules, particularly molecules of biochemical interest, havecharacteristic “fingerprint” absorption spectra in the near infrared.

[0043] The sample is placed adjacent to the output of the interferometerand the detector. The sample absorbs radiation of specific wave lengths.The unabsorbed radiation is reflected back to the detector and recordedas an interferogram. The interferogram is then transformed into a singlechannel spectrum by Fourier Transformation. The background spectrum isthen used to calculate the transmission or absorption of the sample.

[0044] After an interferogram has been collected, a computer performs aFast Fourier Transform (FFT), which results in a frequency domain trace(i.e. intensity vs wavenumber). The detector used in an FT-NIRinstrument must respond quickly because intensity changes are rapid (themoving mirror moves quickly). To achieve a good signal to noise ratio,many interferograms are obtained and then averaged. This can be done inless time than it would take a dispersive instrument to record one scan.

[0045] Advantages of the Fourier Transform Near Infrared Spectrometersover Dispersive Near Infrared Spectrometers include:

[0046] Improved frequency resolution;

[0047] Improved frequency reproduceablity;

[0048] Higher energy throughput;

[0049] Faster operation computer based (allowing storage of spectrafacilities for processing spectra)

[0050] Easily adapted for remote use.

[0051] Scanning of the different types of fats found in subcutaneouslayer of skin using FT-NIR Spectroscopy and taking the second derivativeof the spectra shows different spectral characteristics for the fattyacids or their combination.

[0052] Development of reference samples that contain a matrix thatsimulates the chemical composition of human tissue and containing knownamounts of fatty acids are a significant factor in determining thein-vivo fat content of a human. The reference samples are developed andscanned using a Fibre Optic Probe (10), as illustrated in FIG. 1. Asillustrated in FIG. 1, the Infrared source (12) emits a laser light beamof Near Infrared Radiation (NIR), which is delivered to the test sample(14) via a delivery fibre optic bundle (16). The NIR penetrates thesample (14) and specific wavelengths are absorbed or reflected. Thereflected wavelengths are transmitted to a detector (18) via acollection fibre optic bundle (20). The reflected NIR wavelengths arerecorded as an interferogram. The interferogram is then converted into aspectral reading, integrated, and the resulting data plotted againstknown fat content of the reference samples to create a calibration curveas shown in FIG. 3.

[0053] The methodology used to scan and determine fat content of a humanis preferably as follows:

[0054] Fourier Transform Near Infrared Spectrometer probe (10) is usedto scan the back of ear so that the laser is pointed away from eyes.This is best illustrated in FIG. 2;

[0055] measurements are taken, and as an example, each measurement mayconsist of five scans for a total of less than one minute;

[0056] dependent upon the results, the above step may be repeated;

[0057] following the scanning, data analysis is performed and the fatcontent is determined and recorded.

[0058] Although other parts of the body may be tested for fat content,scans of the ear, as shown in FIG. 2, were found to provide the mostaccurate readings when the results were compared to MRI readings. Theear is convenient, exposed, and has a thin layer of skin over cartilage,rendering the method of the invention convenient, safe and accurate.

[0059] Two different methods to determine the fat content can then beused. In the preferred embodiment, the NIR response, which is directlyrelated to subcutaneous fat content of humans is matched to that ofreference using the calibration curve (FIG. 3). In this embodimentstandard reference samples are created having known concentrations offat. The reference samples are scanned using the FT-NIR spectrometer.The results are then plotted against the known concentration of thereference sample producing the calibration curve of FIG. 3. The linearequation y=76.02×−0.756 is used to determine the subcutaneous fatcontent of humans where y would be the fat content in percent and xwould be the total of the averages of the integration values atdifferent frequencies.

[0060] Another embodiment involves integrating the NIR response ofhumans into an empirical equation (Table 2) taking gender, height,weight, and age into consideration. Both methods have been compared toMRI results to validate accuracy.

[0061] The following Table 1 displays the data for eighteen volunteersbetween the ages of 19 to 49. TABLE 1 Volunteer Data Circ. NIR Fat % byNIR Fat % ID No. Gender Height Weight (cm) Response BMI Circumference¹(Subcutaneous) 1001 M 1.74 79.1 97 0.26 26 21.8 18.74 1002 F 1.65 61.4 —0.46 23 — 33.30 1003 M 1.73 82.5 100 0.29 28 23.7 20.63 1004 M 1.75 61.477 0.15 20 9.4 10.20 1005 M 1.83 79.5 83 0.14 24 13.0 9.23 1006 F 1.6367.3 — 0.38 25 — 27.34 1007 M 1.88 93.0 90 0.07 26 17.4 4.24 1008 M 1.7484.1 94 0.29 28 19.9 20.63 1009 F 1.63 72.0 — 0.26 27 — 18.40 1010 M1.91 95.0 91 0.28 26 17.7 19.89 1011 F 1.56 60.5 — 0.35 25 — 25.10 1012M 1.83 79.5 83 0.24 24 13 16.91 1014 M 1.85 90.0 102 0.23 26.3 24.916.24 1015 F 1.58 54.5 — 0.43 22.0 — 31.21 1016 F 1.65 72.7 — 0.36 26.7— 26.10 1017 M 1.83 68.0 80 0.14 20.3 11.2 9.57 1018 M 1.70 63.6 79 0.2022.0 10.6 13.85 1019 M 1.78 95.4 95 0.31 30.1 20.6 22.25

[0062] Subject 1007 and 1010 show a similar weight and height with asimilar abdominal circumference and have the same BMI. However,according to the NIR fat content measurement, subject 1007 (a bodybuilder) has 15% less fat than subject 1010 (an average male). Theseresults show that BMI can be misleading predictor of human health.

[0063] In the second embodiment an empirical equation is developed todetermine the fat of humans. A certain percentage of fat is distributedsubcutaneously throughout the human body and an empirical formulacalculating the body surface area has been developed. By taking theheight and weight of the subject, the NIR responses and the ratios ofsubcutaneous fat to total fat of each gender and age, the volume ofsubcutaneous fat can be determined and then converted to total fatcontent.

[0064] The original equation to determine body surface area of humanswas formulated in 1916 by Dubois and Dubois based on 9 subjects. Sincethen, several updated formulas have become available. The Gehan andGeorge formula was chosen for this analysis of body fat content as it isa more accurate version of the Mostellar formula, which is widely usedacross Canada as a standard at hospitals and clinics, and was based onthe direct measurement of 401 individuals as compared to the Boydformula which was based on 197 observations.

[0065] An empirical equation was developed using the NIR response, bodysurface area, fat density in humans, gender, age, and ratio ofsubcutaneous to total fat content obtained from MRI studies.

[0066] The empirical equation for total fat for each gender is shownbelow in Table 2. TABLE 2 NIR Empirical Equation for total body fat.Females Males${TBF} = {\frac{64.719N*W^{0.51456}*H^{0.42246}}{\left( {{{- 0.001}A} + 0.989} \right)W}\quad (8)}$

${TBF} = {\frac{64.719N*W^{0.51456}*H^{0.42246}}{\left( {{{- 0.003}A} + 0.9971} \right)W}\quad (9)}$

Examples

[0067] 1. Given:Gender=Male Age=49

[0068] Height=174 cm Weight=77.3 kg

[0069] NIR Response=0.29 $\begin{matrix}{{TBF} = \frac{64.719N*W^{0.51456}*H^{0.42246}}{\left( {{{- 0.003}A} + 0.9971} \right)W}} \\{= \frac{64.719(0.29)*(77.3)^{0.51456}*(174)^{0.42246}}{\left\lbrack {{{- 0.003}(49)} + 0.9971} \right\rbrack (77.3)}} \\{= \frac{18.76851*9.366592802*8.841835596}{65.71273}} \\{= {23.7\%}}\end{matrix}$

[0070] 2. Given:Gender=Female Age=21

[0071] Height=163 cm Weight=67.3 kg

[0072] NIR Response=0.38 $\begin{matrix}{{TBF} = \frac{64.719N*W^{0.51456}*H^{0.42246}}{\left( {{{- 0.001}A} + 0.989} \right)W}} \\{= \frac{64.719(0.38)*(67.3)^{0.51456}*(163)^{0.42246}}{\left\lbrack {{{- 0.001}(21)} + 0.989} \right\rbrack (67.3)}} \\{= \frac{24.59322*8.722147594*8.601234245}{65.1464}} \\{= {28.3\%}}\end{matrix}$

[0073] Comparison of NIR Empirical Equation Results to NIR ReferenceMaterial Results

[0074] A total of 125 volunteers (71 females and 54 males) were scannedand their total body fat content calculated using both the NIR EmpiricalEquation and the NIR Reference Mixture. FIG. 4 displays the NIR resultsfor females and males combined.

[0075]FIG. 4 indicates a strong correlation between the NIR Empiricalequation and the NIR reference mixture. This relationship is also shownin FIGS. 5 and 6.

[0076] Comparison of NIR Results to MRI Results for Volunteers withSimilar Gender, Age, Height and Weight

[0077] The NIR data and MRI data for several volunteers were matchedwith each other according to gender, age, height and weight. The resultsare listed below in Table 3. There are 12 groups each with twoindividuals having similar characteristics. The last two columns inTable 3 show the fat content measured by NIR (equation and referencemixture) and MRI. TABLE 3 Comparison of NIR and MRI Volunteers. MRI MRIWith Height Weight NIR SAT TAT % Fat of Ref. Grp ID No. Gender Age (cm)(cm) BMI Resp (L) (kg) TotalBody Mixture 1 NIR 1006 Female 21 163 67.325.33 0.38 — — 28.32 28.13 MRI 0163 Female 22 165.6 70.9 25.9 — 23.3822.07 31.13 — 2 NIR 1002 Female 24 165 61.4 22.54 0.46 — — 36.15 34.21MIR 0269 Female 25 169 62.7 21.9 — 21.32 20.01 31.92 — 3 NIR 1060 Female27 160 68.2 26.64 0.41 — — 30.22 30.31 MRI 1184 Female 29 157.5 65 26.2— 20.12 19.02 29.26 — 4 NIR 1086 Female 34 163 63 23.71 0.45 — — 34.7633.12 MRI 0218 Female 36 164 63 23.4 — 20.17 19.2  30.47 — 5 NIR 1078Female 42 168 73.6 26.08 0.49 — — 36.31 36.6  MRI 0329 Female 42 167.373.4 26.2 — 27.61 26.8  36.51 — 6 NIR 1066 Female 43 170 72.3 25.02 0.37— — 27.66 27.29 MRI 0107 Female 44 170.8 72.6 24.9 — 23.79 23.01 31.69 —7 NIR 1094 Female 44 158 60.5 24.23 0.41 — — 32.67 30.54 MRI 0343 Female45 158.6 61.6 24.5 — 21.47 21.31 34.59 — 8 NIR 1034 Male 21 185 88.625.89 0.29 — — 20.93 21.57 MRI 0201 Male 20 183.6 89.8 26.6 — 19.9818.98 21.13 — 9 NIR 1018 Male 24 170.2 63.6 21.96 0.2  — — 16.24 14.37MRI 0011 Male 25 172.6 64.5 21 —  8.78  8.39 13.01 — 10 NIR 1031 Male 31175 77.3 25.24 0.23 — — 17.65 16.7  MRI 0315 Male 35 176.9 77.6 24.8 —11.26 11.38 14.67 — 11 NIR 1059 Male 37 180 86.4 26.67 0.24 — — 18.1417.58 MRI 0111 Male 38 181.1 88.3 26.9 — 16.78 16.85 19.08 — 12 NIR 1001Male 49 174 77.3 25.52 0.29 — — 23.66 21.29 MRI 0082 Male 49 174.3 78.125.7 — 13.29 15.78 20.21 —

[0078] The 12 groups of volunteers are displayed in FIG. 7 comparing theMRI results to the NIR Empirical Equation results.

[0079] Although the MRI and NIR tests were performed on differentvolunteers at different times, the correlation between the results ofthe two techniques is remarkable and the similarities are gender neutralin that there are no obvious differences for the male or femalevolunteers. The relationship could be further validated by performingboth tests on the same individual at the same time and location.

[0080] The foregoing is a description of a preferred embodiment of theinvention which is given here by way of example only. The invention isnot to be taken as limited to any of the specific features as described,but comprehends all such variations thereof as come within the scope ofthe appended claims.

What is claimed is;
 1. A method of in-vivo measurement of the fatcontent of a body, the body containing at least one form of fatty acidhaving a reflectance characteristic corresponding to a wave band oflight in the near-infrared region of the spectrum, comprising the stepsof; applying a NIR beam to a selected portion of the body, whereby aportion of the NIR beam is reflected; detecting the reflected beam to adetector; analysing the reflected beam by Fourier Transform techniquesto determine the intensity of the detected beam in at least one waveband selected for its correspondence to a form of fat; comparing theintensity of reflected beam in the at least one wave band with thereflective characteristics of a reference fat in said wave band, andthereby; evaluating the fat content of the body.
 2. A method as claimedin claim 1, wherein the NIR beam is provided by a NIR-source emitting alaser light beam of near infrared wavelengths and passing said laserlight beam through an interferometer to encode data from the wholespectral range simultaneously.
 3. A method as claimed in claim 2,wherein the selected portion of the body has a relatively thin skinlayer over a layer of cartilage.
 4. A method as claimed in claim 3,wherein the NIR beam is delivered to the selected portion of the body bya fibre optic probe.
 5. A method as claimed in claim 4, wherein the atleast one wave band is a narrow wave band and has a spectral resolutionof between 0.3 nm (2 cm⁻¹ at 8000 cm⁻¹) and 2 nm (13 cm⁻¹ at 8000 cm⁻¹).6. A method as claimed in claim 5, wherein the spectral resolution is1.2 nm (8 cm⁻¹ at 8000 cm⁻¹).
 7. A method as claimed in claim 6, whereinthe selected portion of the body having a relatively thin skin layerover a layer of cartilage is the subject's ear.
 8. A method of in-vivomeasurement of the fat content of a body, the body containing at leastone form of fatty acid having a reflectance characteristic correspondingto a narrow wave band of light in the near-infrared region of thespectrum, comprising the steps of; providing a NIR-source emitting alaser light beam of near infrared wavelengths and passing said beamthrough an interferometer to encode data from the whole spectral rangesimultaneously; applying the near infrared light beams through a fibreoptic probe to a selected portion of the body having a relatively thinskin layer over a layer of cartilage; directing the reflected light beamfrom the skin to a detector; analysing the reflected light by FourierTransform techniques to determine the intensity of the light in at leastone narrow wave band selected for its correspondence to a form of fat;comparing the intensity of reflected light in that wave band with thereflective characteristics of a known standard fat in said wave band,and thereby; evaluating the fat content of the body.
 9. An apparatus forscanning a selected body part using FT-NIR for determination of percentbody fat comprising; a NIR-source for emitting a light beam in the nearinfrared spectrum; an interferometer to encode data from the wholespectral range simultaneously, whereby the NIR light beam is passedthrough the interferometer encoding data from the whole spectral rangesimultaneously; a fibre optic probe for delivery of the emitted light tothe selected body part where a portion of the emitted light is reflectedby the body part, the reflected light is collected and transported to adetector.
 10. An apparatus as claimed in claim 9, wherein the fibreoptic probe has a delivery bundle for delivery of the emitted light tothe selected body part and a collection bundle for collection of thereflected light and transport of the reflected light to the detector.